1. Technical Field
This invention relates to a snap-ring supplying device and a snap-ring supplying method for, when a C-shaped snap ring having a gap is automatically fitted into an installation groove formed in a workpiece, such as a piston, supplying the snap ring taken out from a magazine to the workpiece while directing the gap of the snap ring in a predetermined direction. More particularly, this invention relates to a snap-ring supplying device that is used in a step of taking out a snap ring from a magazine and supplying the snap ring to an area in which the snap ring is contracted (i.e., in which the diameter of the snap ring is reduced) and that serves as a part of a snap-ring installing apparatus, and relates to a snap-ring supplying method.
2. Description of the Related Art
Various types of snap-ring installing apparatuses or snap-ring supplying devices have been developed. In a piston of an internal combustion engine, the snap-ring installing apparatus or the snap-ring supplying device is used to automatically fit a snap ring, which is used to prevent a piston pin that connects a connecting rod to the piston from falling off, into an annular installation groove formed in the piston.
In the snap-ring installing apparatus, the lowest one of a plurality of snap rings that are piled together and are contained in a magazine is first cut out (taken out) one by one from the magazine, and the snap ring is then contracted to reduce the diameter thereof. Thereafter, the snap ring is pushed into an installation groove of a piston, and is then snapped back to enlarge the diameter thereof by the elastic restoring force of the snap ring, thus completing installation of the snap ring. In this process ranging from the ring-taking-out step to the ring-fitting step, there is a need to regulate the snap ring so as to direct a gap of the snap ring in a predetermined direction and so as not to deviate the position of the gap.
A conventional apparatus is known as an example of the snap-ring installing apparatus that performs the series of operations. In this conventional apparatus, snap rings are pushed out from a magazine one by one by a reciprocating cutting-out plate (extrusion member) so that a gap of the snap ring is directed forwardly with respect to a direction in which the snap ring is pushed out, are then moved along a conveying path, are further moved while changing the attitude of the snap ring so that the gap of the snap ring pushed out therefrom is directed downwardly by the weight of the snap ring when the snap ring reaches a projection-strip guide wall, and are conveyed to an area in which the snap ring is contracted to reduce the diameter thereof (see Japanese Unexamined Patent Publication No. 2002-346855, for example).
However, in this conventional snap-ring installing apparatus, there is a fear that, in the process ranging from the step of cutting out the snap rings from the magazine to the step of conveying the snap rings to the projection-strip guide wall, the direction of the gap of the snap ring will be deviated, and hence clogging and jamming will occur without engaging the gap with the projection-strip guide wall. Additionally, there is a fear that, if a cover plate or the like is provided above the projection-strip guide wall in order to prevent the intrusion of dust or foreign materials, the snap ring conveyed to the projection-strip guide wall will cling to the cover plate by, for example, the magnetization of the cover plate resulting from a time-dependent change or by an adsorbing action of, for example, an oil film adhering to the cover plate, and will be maintained in a horizontal state without changing the attitude of the snap ring so as to direct the gap downwardly, and hence clogging and jamming will occur.
A conventional snap-ring supplying device is also known. In this device, snap rings are pushed out from a magazine one by one by a cutting-out plate (extrusion member) whose end has a projection, and, simultaneously, the projection of the cutting-out plate is fitted into a gap of the snap ring. The snap rings are then moved along a conveying path while directing the gap backwardly, and are conveyed to a step of contracting the snap ring to reduce the diameter thereof by means of a pushing-up rod that can move in upward and downward directions when the snap ring reaches a predetermined position (see Japanese Unexamined Patent Publication No. 2000-135634, for example).
However, in this snap-ring supplying device, since the gap of the snap ring is not under restrictions (since the gap is not directed to prevent the deviation of the position of the gap) before allowing the cutting-out plate to come into contact with the snap ring, there is a fear that the position of the gap will be deviated by shocks or vibrations given from outside. Additionally, if the snap ring is pushed out in a state in which the gap is directed forwardly in the direction in which the snap ring is pushed out, the gap cannot be directed by the projection of the cutting-out plate situated backwardly, and hence the same problem as in the conventional snap-ring installing apparatus mentioned above will arise.
The present invention has been made in consideration of the foregoing circumstances. It is therefore an object of the present invention to provide a snap-ring supplying device and a snap-ring supplying method capable of, in a simple structure, reliably directing a gap of a snap ring and stably supplying snap rings to fit the snap rings when the whole process ranging from a step of supplying the snap rings to a step of fitting the snap rings is automatically performed.